[rake] Add 'docs:generate' task and make 'docs' a synonym
[rake] Add 'docs:open' task to open in a browser
[appledoc] Document EKEnumerable protocol and each:
[appledoc] Document eachWithIndex:
[appledoc] Document flattenMap: and other minor fixes
[appledoc] Improve mapDictionary: docs with usage, note on duplicate keys
Add test for behaviour of mapDictionary: with duplicate keys
Fix issue in SortedList test helper where self was not returned

SortedList was returning it's data array after enumerating with each:,
breaking encapsulation. Also, instancetype is awesome for catching this.
Add -wrap; wraps a collection of elements in the keys returned by the block